Assessment of exposure to and risk posed by toluene in Japanese residents: combining exposure from indoor and outdoor sources.

Toluene is a chemical substance whose release to the atmosphere is the largest among the pollutant release and transfer registers (PRTR) chemicals and is regarded as one of the major indoor air pollutants. We have developed a method of estimating the distribution of personal exposures of Japanese residents, combining exposure from indoor and outdoor sources. Personal exposure was divided into contributions of indoor and outdoor sources. Ambient toluene concentration was estimated for a 5 x 5 km square grid spatial resolution using the National Institute of Advanced Industrial Science and Technology-atmospheric dispersion model for exposure and risk assessment (AIST-ADMER) using PRTR emission data. The contribution of indoor sources was assumed to be the difference between indoor and outdoor concentrations, which was regarded to have a lognormal distribution. The health risk from toluene exposure in Japanese residents is expressed as the number of people whose personal exposure exceeded the reference values, which were set on the basis of a review of epidemiological studies. Finally, a risk-reduction strategy is suggested according to the proposed principle of risk management.